Detection of materials that are present within another material using x-rays is particularly difficult if the surrounding material has a significantly higher x-ray absorption characteristic. For such cases, higher x-ray energies are required to penetrate and evaluate the surrounding material which can make the materials with low absorption characteristics essentially invisible in the resulting x-ray image.
An example of such a case is the detection of casting core material within the metal structure of aerospace components. While the core material is intended to be completely removed before part usage, a costly neutron radiographic procedure is typically invoked to detect residual core material that would be detrimental to the part if left in the part.
There is a need to be able to detect the presence of material with low x-ray absorption characteristics in the presence of material with high x-ray absorption characteristic in a timely and cost effective manner. In particular, using the method for detection of low x-ray absorption material in conjunction with x-ray inspections already used for inspection of other characteristics of the component such as the presence of voids would provide an especially efficient inspection process.